Game trees (or extensive-form games) were first defined by von Neumann and Morgenstern in 1944. In this paper we examine the use of game trees for representing Bayesian decision problems. We propose a method for solving game trees using local computation. This method is a special case of a method due to Wilson for computing equilibria in 2-person games. Game trees differ from decision trees in the representations of information constraints and uncertainty. We compare the game tree representation and solution (...) technique with other techniques for decision analysis such as decision trees, influence diagrams, and valuation networks. (shrink)

Liver transplantation offers a lifesaving treatment for patients suffering from end-stage liver failure, but not all candidates in the United States are eligible owing to center-specific criteria. When a patient is rejected at a transplantation center for medical, surgical, or psychosocial issues, they are often referred to other centers. We focus on this practice of reevaluation at a second center when the candidate was rejected for psychosocial reasons. We review the criteria used by health professionals to determine psychosocial eligibility and (...) present three case examples from a large teaching hospital that demonstrate this phenomenon in practice. The cases illustrate the conflicts among autonomy, beneficence, nonmaleficence, and justice. We present arguments for and against this practice and provide concrete solutions as a path forward. (shrink)

Repeatedly performing a submaximal motor task for a prolonged period of time leads to muscle fatigue comprising a central and peripheral component, which demands a gradually increasing effort. However, the brain contribution to the enhancement of effort to cope with progressing fatigue lacks a complete understanding. The intermittent motor tasks closely resemble many activities of daily living, thus remaining physiologically relevant to study fatigue. The scope of this study is therefore to investigate the EEG-based brain activation patterns in healthy subjects (...) performing IMT until self-perceived exhaustion. Fourteen participants repeated elbow flexion contractions at 40% maximum voluntary contraction by following visual cues displayed on an oscilloscope screen until subjective exhaustion. Each contraction lasted ≈5 s with a 2-s rest between trials. The force, EEG, and surface EMG data were simultaneously collected. After preprocessing, we selected a subset of trials at the beginning, middle, and end of the study session representing brain activities germane to mild, moderate, and severe fatigue conditions, respectively, to compare and contrast the changes in the EEG time-frequency characteristics across the conditions. The outcome of channel- and source-level TF analyses reveals that the theta, alpha, and beta power spectral densities vary in proportion to fatigue levels in cortical motor areas. We observed a statistically significant change in the band-specific spectral power in relation to the graded fatigue from both the steady- and post-contraction EEG data. The findings would enhance our understanding on the etiology and physiology of voluntary motor-action-related fatigue and provide pointers to counteract the perception of muscle weakness and lack of motor endurance associated with ADL. The study outcome would help rationalize why certain patients experience exacerbated fatigue while carrying out mundane tasks, evaluate how clinical conditions such as neurological disorders and cancer treatment alter neural mechanisms underlying fatigue in future studies, and develop therapeutic strategies for restoring the patients' ability to participate in ADL by mitigating the central and muscle fatigue. (shrink)

Disorders of sexual development are a heterogeneous group of disorders in which chromosomal, gonadal or anatomical sex development is atypical. The majority of these children are recognized at birth by ambiguous genitalia. Legal and societal pressures require the physician and parents to assign sex rapidly. Though sex assignment is undebated in several disorders of sexual development, many others need an individualized approach to gender-related concerns. Gender dysphoria is prevalent in disorders of sexual development, and early gender-defining surgeries have potentially lifelong (...) consequences. We use two cases, one of partial androgen insensitivity and another of simple virilizing congenital adrenal hyperplasia to illustrate that in disorders of sexual development, the ethical management principles remain the same at their core despite the vast differences in phenotypes. Sex assignment should maximize functional, psychological and sexual needs. Sex assigned should coincide with gender identity. We propose that we manage such children with the mutual participation of the physician, parents and the child. Though the parents and the physician have the child's best interests when making a decision, the child's developing autonomy should be protected. The communication of the health provider to the parent must be honest if early sex assignment is difficult. (shrink)

Brams’ paradox of new members and Shenoy’s paradox of smaller coalitions are, in a sense, equivalent. They are both implied by the monotonicity of a power index: while the first is exhibited on every simple game that is not strong, the latter can be observed on every simple game in which players are not almost symmetric. For the Shapley–Shubik index, this symmetry condition is not only necessary but also sufficient to avoid the paradox of smaller coalitions.